The short version
Measure, convert to cubic feet, divide weight by that figure, then read the class off the table. A 200 lb shipment on a 40 x 48 x 40 inch pallet works out to about 44.4 cubic feet, giving 4.5 PCF, which maps to class 200. Everything past this point is detail on how to get that number right the first time.
Step-by-step: from measurements to class
- Measure length, width, and height of the shipment in inches, pallet and packaging included.
- Convert to cubic feet: length times width times height, divided by 1,728.
- Divide total weight in pounds by cubic feet to get density in pounds per cubic foot.
- Find the density range in the class chart that matches your PCF figure.
Worked example
Shipment: 500 lbs on a 48 x 40 x 60 inch pallet, freight included.
Volume: 48 × 40 × 60 ÷ 1,728 = 115,200 ÷ 1,728 = 66.67 cubic feet.
Density: 500 ÷ 66.67 = 7.5 PCF. Class: 125.
When density is not the final word
The NMFC manual contains thousands of specific item numbers, each with a fixed class. Household goods, hazmat materials, and many specialty commodities fall into this category. When an item number applies, those commodities carry a fixed class that a density calculation will not match. The density method is the most reliable general approach, but it is not universal, so check the item number for anything unusual before you quote a rate off the density table alone.
What happens if you get the class wrong
Carriers can inspect freight at delivery and reclassify it on the spot. The billing adjustment arrives separately, sometimes weeks after the shipment delivered. On high-class freight, that adjustment can be significant. Getting the class right up front avoids invoice surprises and carrier disputes, which matters more the more often the same commodity ships.
The safest habit is to keep a short record for anything you ship regularly: weight, dimensions, calculated PCF and the class that history has actually billed you at. When a carrier's number does not match your own log, that gap is worth a phone call before you accept the adjustment, not after.
Skip the manual steps
Type in weight and dimensions and the tool returns class, density and an estimated cost range.